Temperature-responsive switch assemblies

ABSTRACT

Temperature-responsive switch assemblies including a control member controlling the position of a movable contact with respect to a stationary contact, the control member being constructed of a material having a temperature-actuated shape memory and having an initial shape and a distorted shape, means biasing the movable contact into one position when the control member has the distorted shape, and temperature control means for reverting the control member to the initial shape to move the movable contact to another position.

United States Patent James R. Willson Garden Grove;

Keith T. Krueger, Garden Grove; Hugh J. Tyler, Santa Ana; Wilbur F.Jackson, Rolling Hills, all of Calif.

[72] Inventors 1211 Appl. No. 843,723

[22] Filed July 22, 1969 [45] Patented Jan. 11, I972 [73 AssignccRobertshaw Controls Company Richmond, Va.

[54] TEMPERATURE-RESPONSIVESWITCH ASSEMBLIES 28 Claims, 8 Drawing Figs.

[52] 0.8. CI 337/123, 337/140, 337/382, 337/393 [51] Int. Cl l-l0lh37/46, HOlh 61/00 [50] Field of Search 337/123,

Primary Examiner- Bernard A. Gilheany Assistant ExaminerDewitt Mr MorganAttorney-Anthony A. OBrien, Auzville Jackson &

Robert L. Marben ABSTRACT: Temperature-responsive switch assembliesincluding a control member controlling the position ofa movable contactwith respect to a stationary contact, the control member beingconstructed of a material having a temperature-actuated shape memory andhaving an initial shape and a distorted shape, means biasing the movablecontact into one position when the control member has the distortedshape,

[56] References Cited and temperature control means for reverting thecontrol UNlTED S A E T N S member to the initial shape to move themovable contact to 3,516,082 6/1970 Cooper, 337/140 ux a I8 713- 36 f$l6 m 50 4o l l4 46 1 L 12 In 26 l 44 K523 ai \\i\\\\\\\\\\ 48 PATENTEDJAN] 1 1912 3,634,803

SHEET 2 BF 2 444 446 ,310 FIG.5

436 326 322 S 324 gig k 3% 354 3'8 340 330 ssrfi am 328 vvv v v 736 ,724INVENTORS.

q 734 James R Willson 72a I Keith T. Krueger T- 722 740 732 Hugh J.Tyler 738 BY Wilbur F. qockson ATTORNEY TEMPERATURE-RESPONSIVE SWITCHASSEMBLIES BACKGROUND OF THE INVENTION The'present invention pertains totemperature-responsive switch assemblies and more particularly to switchassemblies including a control member constructed of a material havingamodulus of elasticity varying with temperatureto provide atemperature-actuated shape memory.

Many types of temperature-responsive switchassemblies have been used inthe past for various electrical control purposes. Such switch assembliesnormally utilize temperature responsive operators such as bimetals,hydraulic bulbs and bellows, and expansible rods and tubes; however, allof these conventional operators have sufiered from common disadvantages.The major disadvantage in using conventional temperature-responsiveoperators is that the amount of work obtained from the amount of energysupplied by way of heat is low thereby providing inefficient operation.Furthermore, conventional temperature-responsive operators havestandardized invariable shapes and cross sections andare not adaptableto new and varying switch assembly applications.

Generally, conventional temperature-responsive operators operate byexpansion and contraction; that is, in the case of a bimetal, thevarying coefficient of expansion of the two strips of metal secured toeach other causes deflection of the bimetal; and in the case of a rodand tube, the rod is constructed of a metal having a low coefficient ofexpansion and is secured at one end to the tube which has a much highercoefficient of expansion such that the rod is moved by the tube: inresponse to temperature.

Since conventional temperature-responsive switch assemblies utilizeoperators that are dependent upon the expansion and contraction ofmaterials they require ambient tempera-:

ture compensation in order to prevent inaccurate and faulty operation.Complete ambient temperature compensation is difficult to provide; and,accordingly, the need for ambient temperature compensation is a distinctdisadvantage.

SUMMARY OF THE INVENTION It is an object of the present invention to.construct a temperature-responsive switch assembly utilizing a materialhaving a temperature-actuated shape memory.

Another objectof the present invention is to utilize a control memberconstructed of a material having a temperaturestate of theswitchassembly.

A further object of the present invention is to utilize a spring 1constructed of a material having a temperature-actuated shape memory tocontrol a switch assembly.

The present invention has another object in that a .torsion' barconstructed of a material having a temperature-actuated shape memory isutilized to control a switch assembly.

Another object of the present invention is to utilize a wire constructedof a material having a temperature-actuated shape memory to control aswitch assembly.

Switch assemblies constructed in accordance with the present inventionare advantageous over conventional switch assemblies in that a high workoutput is obtained for the amount of energy supplied to the switchoperators by way of I temperature change. The switch operators may. becon-- structed for fail-safe operation such that a set in the switchoperators or breakage of switch operators returns the switch assembly toits normal state, the. switch 'operatorsmay have many differentconfigurations and cross sections, operation of the switch assemblies issilent, and no ambient temperature compensation is required for theswitch assemblies.

The present invention is generally characterized in atemperature-responsive switch assembly'including -a switch hous-.

ing, a stationary contact secured to the switch housing, a

movable contact having-a position in contact with the stationary contactand a position spaced from the stationarycontact, means biasing themovable contact toward one of the positions and operator meanscontrolling the position of the movable contact, the operator meansincluding a control member having an initial shape and a distorted shapeand being constructed of a material having a temperature-actuated shapememory, the movable contact being in the one position when the controlmember has the distorted shape and in the otherposition when the controlmember has the initial shape, and means controlling the temperature ofthe control member to control the shape of the control member.

Further'objects and advantagesoi the present invention will becomeapparent from the description of :the preferred embodiments as shown inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational viewpartially in section of an embodiment of the present invention.

FIG. 2 is an elevational view partially in section of a modification-ofthe embodiment of FIG. I.

FIG. 3 is an elevational view partially in section of a furthermodification of the embodiment of FIG. 1.

FIG. 4 is an elevational view partially in'section of another embodimentof the present invention.

FIG. 5 is an elevational view partially in section of a modification ofthe embodiment of FIG. 4.

FIG. 6 is a broken perspective view of a further embodiment of thepresent invention.

FIG. 7 is a broken perspective view of another embodiment of the presentinvention.

FIG. 8 is an elevational view partially in section of a furtherembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS All of the embodiments of.thepresent invention utilize control members constructed from a materialhaving a temperature actuated shape memory. By this is meant that astraight wire of such a material can be bent or contorted below itsmartensitic" transition temperature and it will retain its deformed ordistorted shape, but when the deformed wire is heated above itstransition temperature with nothing constraining its movement such wirewill spring back to its initial straight shape.

Similarly, the wire may have a loop in it in its initial annealedshapeabove the transition temperature. After annealing the temperaturemay be decreased below the transition temperature, and a load such as aweight secured to the lower end of the wire. The modulus of elasticity,being dependent on temperature, is low at this time; and, accordingly,the weight distortsthe wire from its initial .shape to a straight ordistorted shape: The wire will remain in this condition until thetemperaturesensed by the member is raised above the transitiontemperature at which time the modulus of elasticity will increase; and,once the modulus of elasticity is such that the amount of force orstress applied by the weight is out of relation with .the distortion orstrain, the wire will revert to its initial-looped shapetherebyproviding work in lifting the weight.

The transition temperature is represented by a rapid change in moduluson a modulus of elasticity vs. temperature curve. That is, astemperature decreases through the transition zone, the modulus ofelasticity decreases. As temperature increases throughthe'transitionzone the. modulus of elasticity increases. For'the purposes of theinvention of this disclosure, material with a relatively high transitiontemperature. should be used. This will allow the shape memory materialto cool to a temperature below its transition zone when used at normaloperating ambient temperature. These operating ambients will generallybe greater than room temperature.-

One of the great advantages of the present invention is that thematerial may=be utilized to form control members having greatly varyingshapes and cross sectionsQsuch as rods, flat bars, torsion. bars,helical springs, flat springs, wave washers, spring washers, bellevillesprings, hair springs, or wires, to

name a few. Accordingly, the use of wires has been described only toprovide an understanding of the operation of control members constructedof a material having a temperature-actuated shape memory, and it isclear that control members for use with the present invention may haveany desired shape and cross section as will be appreciated from thefollowing description of the preferred embodiments.

The above description of materials useful with the present invention isprovided for general background in order to aid in understanding thepresent invention. For specific information with respect to one suchmaterial, reference is made to US. Pat. No. 3,174,851 to Buehler et al.and U.S. Pat. No. 3,403,238 to Buehler et al. The above-cited patentsare concerned with alloys formed of nickel and titanium; however, whilean alloy having a composition of 55 percent nickel by weight with theremainder being essentially titanium may be used with the presentinvention, the present invention is not limited to these alloys but mayutilize any materials having similar properties. That is, any materialhaving a temperatureactuated shape memory or a modulus of elasticitythat varies with temperature may be used with the present invention.

A first embodiment of the present invention is illustrated in FIG. 1 andincludes a switch assembly housing constructed of an electricallynonconductive material. The switch assembly includes a stationarycontact 12 secured to a step support on a sidewall of housing 10 and amovable contact 14 secured to the underside of a first end 16 of a lever18 which is supported at its center by a fulcrum 20 secured to a bottomwall of housing 10. A second end 22 of lever 18 has an ear 24 secured tothe underside thereof and insulated therefrom, and an aperture 26 isprovided in car 24. An ear 28, having an aperture 30 therein, is securedto the bottom wall of housing 10 directly below the second end 22 oflever 18, and a spring control member 32 is mounted in tension betweencars 24 and 28 by having one end booked through aperture 24 and theother end hooked through aperture 30. A helical bias spring 34 ismounted in compression between a top wall of housing 10 and the firstend 16 of lever 18.

A pair of terminals 36 and 38 extend through a sidewall of housing 10and are adapted to be connected to a source of electricity and anycircuitry or components for which it is desired to control theapplication of electricity through the switch assembly. Terminal 36 isconnected with stationary contact 12 through a wire 40, and terminal 38is connected with movable contact 14 through a wire 42. A pair ofterminals 44 and46 extend through an opposite sidewall of housing 10 andare adapted to be connected with a source of electricity through aselective control such as a thermostat. Terminals 44 and 46 areconnected with ears 24 and 28 through wires 48 and 50, respectively.

Spring control member 32 is constructed of a material having atemperature-actuated shape memory and has a tightly coiled initial shapeand a loosely coiled distorted shape.

The switch assembly is illustrated in FIG. 1 in its normally closedstate with movable contact 14 normally in contact with stationarycontact 12 due to the force from bias spring 34, and control member 32is in its distorted shape at this time since nonnal room temperatureexists and the modulus of elasticity is low.

When it is desired to open the switch assembly, electricity is appliedto terminals 44 and 46, for instance, by the closing of the selectivecontrol between terminals 44 and 46 and the source of electricity toraise the temperature sensed by spring control member 32. Theapplication of electricity to terminals 44 and 46 causes a current toflow through wire 48, car 24, spring control member 32, ear 28 and wire50. The current passing through spring control member 32 generates heatto increase the modulus of elasticity of spring control member 32, andspring control member 32 will revert to its initial shape once themodulus of elasticity has been increased to a point where the loadconstituted by the force from bias spring 34 is insufficient to distortspring control member 32 to the extent required to maintain contacts 12and 14 closed. Thus,

movable contact 14 will be moved to a position spaced from stationarycontact 12 due to the action of lever 18 about fulcrum 20 when springcontrol member 32 reverts to its initial shape.

When it is desired to return the switch assembly to its normally closedstate, the supply of electricity to terminals 44 and 46 is interruptedthereby stopping the flow of current through spring control member 32and reducing the temperature sensed by spring control member 32 todecrease the modulus of elasticity. Once the modulus of elasticitydecreases to a point where the force from bias spring 34 is sufficientto distort spring control member 32, spring control member 32 assumesits distorted shape to close contacts 12 and I4 and return the switchassembly to its normally closed state.

The embodiment of FIG. 1 is illustrated as a nonnally closed switch,however, it should be clear that the operation of the embodiment of FIG.1 as a normally open switch requires merely the reversing of forces onlever 18, for instance, as shown in phantom in FIG. 1. That is, bymounting bias spring 34 in compression between the bottom wall ofhousing 10 and the underside of the first end 16 of lever 18 andmounting spring control member 32 in tension between the upper side ofthe second end 22 of lever 18 and the top wall of housing 10, theoperation of the embodiment of FIG. 1 will be such that contacts 12 and14 will be normally spaced; and, once spring control member 32' revertsto its initial tightly coiled shape, contacts 12 and 14 will be closed.Of course, the embodiment of FIG. 1 may be modified in many other waysto operate as a nonnally open switch, such as by merely transposingspring control member 32 and bias spring 34.

A modification of the embodiment of FIG. I is illustrated in FIG. 2.Parts in FIG. 2 identical to parts in FIG. I are given identicalreference numbers and are not described again, and similar parts aregiven reference numbers with added.

The primary difference between the embodiments of FIGS. 1 and 2 is thatthe downward force on the second end 22 of lever 18, which is suppliedby spring control member 32 mounted in tension in FIG. 1, is supplied bya spring control member 132 mounted in compression between the upperside of the second end 22 of lever 18 and the top wall of housing 10.Spring control member 132 is constructed of a material having atemperature-actuated shape memory and has a loosely coiled initial shapeand a tightly coiled distorted shape.

The switch assembly is illustrated in FIG. 2 in its normally closedstate with movable contact 14 normally in contact with stationarycontact 12 due to the force from bias spring 34. The operation isidentical to that described with respect to the embodiment of FIG. 1except for the variance in the position and shapes of spring controlmember 132. That is, spring control member 132, as illustrated, isloosely coiled in its initial shape such that once electricity issupplied to terminals 44 and 46 to pass a current through spring controlmember 132, it forces the second end 22 of lever 18 down to compressbias spring 34 and open contacts 12 and 14. In order to return theswitch assembly to its normally closed state, the electricity applied toterminals 44 and 46 is interrupted such that spring control member 132cools and returns to its distorted shape to close contacts 12 and 14 andreturn the switch assembly to its normally closed state.

In the same manner as mentioned with respect to the embodiment of FIG.1, the embodiment of FIG. 2 may be modified to operate as a normallyopen switch by merely reversing the forces on lever 18 as shown inphantom in FIG. 2 with spring control member 132' and bias spring 34' orby transposing spring control member 132 and bias spring 34.

Another modification of the embodiment of FIG. 1 is illustrated in FIG.3. Parts in FIG. 3 identical to parts in FIG. 1 are given identicalreference numbers and are not described again, and similar parts aregiven reference numbers with 200 added.

The forces acting on lever 18 are all located at the second end 22 ofthe lever with a helical bias spring 234 mounted in compression betweenthe upper side of the second end 22 and a top wall of housing and aspring control member 232 mounted in compression between the undersideof the second end 22 and a bottom wall of housing 10.-Spring controlmember 232 is constructed of a material having a temperature-actuatedshape memory and has a loosely coiled initial shape and a tightly coileddistorted shape.

An upright 201 extends from the bottom wall of housing 10 and supports aheating element 203 within spring control member 232. Heating element203 is connected with a pair of terminals 244 and 246 which extendthrough the bottom wall of housing 10 and are adapted to be connectedwith a source of electricity through a selective control.

The switch assembly is illustrated in FIG. 3 in its normally open statewith movable contact 14 spaced from stationary contact 12 due to theforce from bias spring 234. At this time control member 232 is in itsdistorted shape since normal room temperature exists and the modulus ofelasticity is low.

When it is desired to close the switch assembly, electricity is appliedto terminals 244 and 246 to energize heating element 203. The heatgenerated by heating element 203 raises the temperature sensed by springcontrol member 232 and the modulus of elasticity increases with therising temperature. Once the modulus of elasticity has been increased toa point where the load constituted by the force from bias spring 234 isinsufiicient to distort spring control member 232, spring control member232 will revert to its initial shape thereby pushing the second end 22of lever 18 up to accordingly move the first end 16 of the lever down toplace movable contact 14 in contact with stationary contact 12.

When it is desired to return the switch assembly to its normally openstate, the supply of electricity to terminals 244 and 246 is interruptedthereby deenergizing heating element 203 and reducing the temperaturesensed by spring control member 232. The modulus of elasticity, thus,decreases until a point is reached where the force from bias spring 234is sufficient to distort spring control member 232. Spring controlmember 232 will then assume its distorted shape, and the second end 22of lever 18 will be pushed down to open contacts 12 and 14. v i

If it is desired to operate the embodiment of FIG. 3 as a normallyclosed switch the forces on the second end 22 of lever 18, need merelybe reversed. For instance, by transposing spring control member 232 andbias spring 234 the switch assembly may have a nonnally closed mode ofoperation.

Another embodiment of the present invention is illustrated in FIG. 4 andincludes a switch assembly housing 310 constructed of an electricallynonconductive material. The switch assembly includesa stationary contact312 secured to a step support on a sidewall of housing 310 and a movablecontact 314 secured to the underside of a first end 316 of an elongatedleg of a lever 318. Lever 318 is supported by a fulcrum 320 and has ashort offset leg 322 having a pair of ears 324 and 326 disposed oneither side thereof. A bias spring 328 is mounted in tension between anaperture 330 in car 324 and an aperture 332 in an ear 334 secured to abottom wall of housing 310. A single-strand wire control member 336 hasa first end secured to a sidewall of housing 310 by a screw 338 and asecond end secured to an aperture 340 in ear 326. A heating coil 340 isdisposed around wire control member 336 andis connected with a pair ofterminals 344 and 346 which extend through a top wall of housing 310 andare adapted to be connected to a source of electricity throughaselective control.

A pair of terminals 348 and 350 extend through the sidewall of housing310 and are adapted to be connected to a source of electricity and anycircuitry or components for which it is desired to control theapplication of electricity through the switch assembly. Terminal 348 isconnected with stationary contact 312 through a wire 352, and terminal350 is connected with movable contact 314 through a wire 354.

Single-strand wire control member 336 is constructed of a materialhaving a temperature-actuated shape memory and has a short effectivelength between ends in its initial shape and a longer effective lengthbetween ends in its distorted shape. The initial shape of wire controlmember 336 may be linearly shorter than the wire control member in itsdistorted shape or may have a loop or other curvature to reduce theeffective length between the ends of the wire control member.

The switch assembly of FIG. 4 is illustrated in its normally open statewith movable contact 314 spaced from stationary contact 312 due to theforce from bias spring 328. At this time wire control member 336 is inits distorted shape since normal room temperature exists and themodulus'of elasticity is low.

When it is desired to close the switch assembly electricity is appliedto terminals 344 and 346 to energize heating element 342. The heatgenerated from heating element 342 raises the temperature sensed by wirecontrol member 336 to increase the modulus of elasticity; and, once themodulus of elasticity has been increased to a point where the loadconstituted by the force from bias spring 328 is insufficient to distortwire control member 336, the wire control member will revert to itsinitial shape. Thus, movable contact 314 will be moved to a position incontact with stationary contact 312 due to the action of lever 318 aboutfulcrum 320 when wire control member 336 reverts to its initial shape.

When it is desired to return the switch assembly to its normally openstate the supply of electricity to terminals 344 and 346 is interruptedto deenergize heating element 342 and reduce the temperature sensed bywire control member 336. The modulus of elasticity of wire controlmember 336 decreases with the decrease in temperature; and, once themodulus of elasticity decreases to a point where the force from biasspring 328 is sufficient to distort wire control member 336, the wirecontrol member assumes its distorted shape to open contacts 312 and 314and return the switch assembly to its normally open state.

If it is desired to operate the embodiment of FIG. 4 as a normallyclosed switch, the forces on lever 318 need only be reversed. Forinstance, by transposing bias spring 328 and wire control member 336,the embodiment of FIG. 4 may be provided with a normally closed mode ofoperation.

A modification of the embodiment of FIG. 4 is illustrated in FIG. 5.Parts in FIG. 5 identical to parts in FIG. 4 are given identicalreference numbers and are not-described again, and similar parts aregiven reference numbers with added.

The primary difference between the embodiments of FIG. 4 and 5 are thata double-strand wire control member 436 is utilized, and the temperaturesensed by wire control member 436 is controlled by passing an electricalcurrent therethrough. Wire control member 436 has both ends secured to asidewall of housing 310 by screws 438 and 439 to define two lengths anda center portion freely movable through aperture 340 in ear 326 suchthat the forces on wire control member 436 are evenly distributed. Wirecontrol member 436 is constructed of a material having atemperature-actuated shape memory and has an initial shape in which theeffective length between the center portion and the ends is short and adistorted shape in which the effective length between the center portionand the ends is long. As mentioned with respect to the embodiment ofFIG. 4, this may be accomplished linearly or with loops. A pair ofterminals 444 and 446 are connected with the two ends of wire controlmember 436, respectively, and extend through a top wall of housing 310.

The switch assembly is illustrated in its normally open state in FIG. 5;and, in order to close the switch assembly, electricity is applied toterminals 444 and 446 to pass a current through both lengths of wirecontrol member 436. The current passing through wire control member 436raises the temperature sensed thereby to accordingly increase themodulus of elasticity; and, once the modulus of elasticity has increasedsufficiently to overcome the force from bias spring 328, wire controlmember 436 reverts to its initial shape to move lever 318 about fulcrum320 to close contacts 312 and 314.

When it is desired to open the switch assembly, the electricity appliedto terminals 444 and 446 is interrupted to decrease the temperature ofwire control member 436 and accordingly decrease the modulus ofelasticity. Once the modulus of elasticity has decreased sufficiently,bias spring 328 will return wire control member 436 to its distortedshape and move lever 318 to open contacts 312 and 314 and return theswitch assembly to its normally open state.

If it is desired to provide the embodiment of FIG. with a nonnallyclosed mode of operation, the forces on lever 318 need only be reversedsuch as by transposing wire control member 436 and bias spring 328 aspreviously described with respect to the embodiment of FIG. 4.

A further embodiment of the present invention is illustrated in FIG. 6and includes a switch assembly housing 510 constructed of electricallynonconductive material. The switch assembly includes a stationarycontact 512 secured to a post at a sidewall of housing 510 and a movablecontact 514 disposed on an arm 516 which is secured to a torsion controlmember 518. Torsion control member 518 is rigidly attached to a block520 at another sidewall of housing 510 by means of a screw 522. Aheating element 524 is disposed around torsion control member 518 and isadapted to be connected to a source of electricity through a selectivecontrol. A bias spring 526 is mounted in compression between a bottomwall of housing 5 l0 and the underside of arm 516. A pair of wires 528and 530 are electrically connected with contacts 512 and 514,respectively, and are adapted to be connected to a source of electricityand any circuitry or components for which it is desired to control theapplication of electricity through the switch assembly.

Torsion control member 518 is a bar or rod constructed of a materialhaving a temperature-actuated shape memory and has a high torsioninitial shape such that it is twisted clockwise as shown in FIG. 6 and alow torsion distorted shape such that it is twisted slightlycounterclockwise from its initial shape.

The switch assembly of the embodiment of FIG. 6 has a normally closedstate; however, it is illustrated in FIG. 6 in its open state. In itsnormally closed state contacts 512 and 514 are in contact due to theforce from bias spring 526. At this time torsion control member 518 isin its low torsion distorted shape since normal room temperature existsand the modulus of elasticity is low.

In order to open the switch assembly, heating element 524 is energizedto raise the temperature sensed by torsion control member 518 andincrease the modulus of elasticity. Once the modulus of elasticity hasincreased to a point where the load constituted by the force from biasspring 526 is insufficient to distort the torsion control member to theextent required to maintain contacts 512 and 514 closed, torsion controlmember will revert to its initial high torsion shape by twistingclockwise to thereby open contacts 512 and 514.

In order to return the switch assembly to its normally closed state,heating element 524 is deenergized to decrease the temperature sensed bytorsion control member 518 and accordingly decrease the modulus ofelasticity. Once the modulus of elasticity decreases to a point wherethe force from bias spring 526 is sufficient to distort torsion controlmember 518, the torsion control member assumes its distorted shape toclose contacts 512 and 514 and return the switch assembly to itsnormally closed state.

In order to provide the embodiment of FIG. 6 with a normally open modeof operation, it is merely necessary to alter the forces on arm 516 suchthat torsion control member 518 twists counterclockwise to its initialshape and bias spring 526 biases the end of arm 516 down away fromstationary contact 512.

Another embodiment of the present invention is illustrated in FIG. 7 andincludes a switch assembly housing 610 constructed of an electricallynonconductive material. The switch assembly includes a stationarycontact 612 secured to a support on a sidewall of housing 610 and amovable contact 614 secured to a step on the sidewall of housing 610 bya linear flexible bar 616. A spring control member 618 has a squaredcenter portion 620 connected with the underside of the end of flexiblebar 616 and two side portions 622 and 624 coiled in opposite directionson a rod 626 supported by the sides of housing 610. The ends of coiledside portions 622 and 624 are secured to housing 610 by means of screws628 and 630. respectively.

A pair of wires 632 and 634 are electrically connected with contacts 612and 614, respectively, and are adapted to be connected to a source ofelectricity and any circuitry or components for which it is desired tocontrol the application of electricity through the switch assembly. Apair of wires 636 and 638 are connected with the ends of spring controlmember 618 and are adapted to be connected with a source of electricitythrough a selective control.

Spring control member 618 is constructed of material having atemperature-actuated shape memory and has a loosely coiled initial shapeand a tightly coiled distorted shape such that the center portion 620rotates counterclockwise as the spring control member reverts from itsdistorted shape to its initial shape as viewed from the right of FIG. 7.

The switch assembly is illustrated in its normally open state withmovable contact 614 spaced from stationary contact 612 due to thetendency of flexible bar 616 to remain linear. At

this time control member 618 is in its distorted shape since normal roomtemperature exists and the modulus of elasticity is low.

In order to close the switch assembly electricity is supplied to wires636 and 638 to pass a current through control member 618 and accordinglyraise the temperature thereof. The modulus of elasticity increases withthe rising temperature until it reaches a point where the loadconstituted by the force from flexible bar 616 is insufficient todistort control member 618 to the extent required to maintain contacts612 and 614 open. At this time spring control member 618 reverts to itsinitial shape with a counterclockwise movement to move contact 614 up tocontact stationary contact 612.

In order to return the switch assembly to its nonnally open state thesupply of electricity to wires 636 and 638 is interrupted to stop theflow of current through spring control member 618 and decrease thetemperature. The modulus of elasticity decreases with the temperatureuntil the force of flexible bar 616 overcomes spring control member 618to return it to its distorted shape thereby opening contacts 612 and 614and returning the switch assembly to its normally open state.

In order to utilize the embodiment of FIG. 7 in a normally closed modeof operation, it is necessary only to reverse the forces on movablecontact 614 such that flexible bar 616 tends to close the contacts andspring control member 618 tends to open the contacts in its initialshape.

A further embodiment of the present invention is illustrated in FIG. 8and includes a switch assembly housing 710 constructed of anelectrically nonconductive material. The switch assembly includes astationary contact 712 secured to a block at a comer of housing 710 anda movable contact 714 secured to the end of a control member 716 whichhas its other end fastened to a step at a sidewall of housing 710. Aheating element 718 is disposed around control member 716 and iselectrically connected to a pair of terminals 720 and 722 which extendthrough a bottom wall of housing 710 and are adapted to be connected toa source of electricity through a selective control. A pair of terminals724 and 726 extend through opposite sidewalls of housing 710 and areelectrically connected to contacts 712 and 714 through a wire 728 and awire 730 and control member 716, respectively.

A bias spring 732 is mounted in tension between the bottom wall ofhousing 710 and the underside of control member 716 with one endconnected to an aperture 734 in an ear 736 secured to control member 716below contact 714 and another end connected to an aperture 738 in an ear740 secured to the bottom wall of housing 710.

' Control member 716 is a bar or rod constructed of a material having atemperature-actuated shape memory and has an upwardly curved initialshape and a linear distorted shape.

The switch assembly is illustrated in its normally open condition inFIG. 8 with movable contact 714 spaced from stationary contact 712 dueto the force from bias spring 732. At this time control member 716 is inits linear distorted shape since normal room temperature exists and themodulus of elasticity is low.

In order to close the switch assembly, electricity is applied toterminals 720 and 722 to energize heating element 718 and raise thetemperature sensed by control member 716. The modulus of elasticityincreases with the rising temperature; and, once the modulus ofelasticity is increased to a point where the load constituted by biasspring 732 is insufficient to distort control member 716 to the extentrequired to maintain contacts 712 and 714 open, control member 716 willrevert to its initial upwardly curved shape to close contacts 712 and714.

In order to return the switch assembly to its normally open state, thesupply of electricity to terminals 720 and 722 is interrupted todecrease the temperature sensed by control member 716. Accordingly, themodulus of elasticity is decreased until a point is reached where theforce from bias spring 732 is sufficient to cause control member 716 toreturn to its linear distorted shape to open contacts 712 and 714.

If it is desired to provide the embodiment of FIG. 8 with a normallyclosed mode of operation, the bias spring may be mounted in compressionbetween a top wall'of housing 710, and control member 716 may be formedwith a linear initial shape and an upwardly curved distorted shape.

The embodiments of FIG. 3, 4, 6 and 8 have the advantage that theheating elements may be varied with respect to electricalcharacteristics to permit the use of the switch assembly with varioussystems and selective controls. Furthermore, when auxiliary heatingelements are utilized no specific electrical characteristics arerequired for the control members thereby permitting the control membersto be sized for optimum operation. While the embodiments of FIGS. 1, 2,and 7 must be precisely matched to various systems and selectivecontrols with respect to the electrical characteristics of the controlmembers, these embodiments have the advantages of reduction ofcomponents, rapid heating, and sensitivity to small operating currentsdue to the passing of the current through the control members tointernally generate heat.

Any of the above-described embodiments may be modified with respect tothe temperature-controllingmeans by merely adding a heating element orpassing a current through the control member in accordance with desiredoperation and the system in which the switch assembly is to be utilized.

The spring control members illustrated in FIGS. 1, 2, 3, and 7 areparticularly adaptable for use with low power because the coiledconfiguration reduces heat loss and permits adjacent coils to heat eachother. The advantages of spring control members can be increased byutilizing a barrel configuration to minimize stress at the spring endswhere the load carrying capacity is less due to the fact that the endsof the spring control member will heat less than the center.

The control members illustrated in the above-identified embodiments arenot meant to be the only shapes, configurations and cross sections ofcontrol members that can be utilized with the present invention. Almostany form of control member can be utilized as long as it will deflectwith a load, such as a spring, and can be heated by current or anauxiliary heating element.

The control members for the embodiments above described may be formed byannealing the material in its initial shape in a position that willeffect the normally closed or normally open mode of operation desiredfor the switch assembly. The annealing step may be performed in theswitch assembly or external of the switch assembly. After annealing,which may be accomplished by passing a current through the controlmember and adjusting the annealed control member, a force is applied tothe control member below the transition temperature to stretch andstabilize the control member. The control member is thus cycled throughits initial and distorted shapes, and the switch assembly is ready foroperation.

In as much as the present invention is subject to many variations,modifications and changes in detail, it is intended that all matterdescribed in the foregoing specification or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. An electrically operated switch assembly comprising a switch housing;

a stationary contact secured to said housing;

a movable contact disposed adjacent said stationary contact and having afirst position in contact with said stationary contact and a secondposition spaced from said stationary contact;

said stationary contact and said movable contact being electricallyconnected in a first electrical circuit having a first operative statewhen said movable contact is in said first position and a secondoperative state when said movable contact is in said second position;

operator means mounted within said housing and connected with saidmovable contact, said operator means including a control memberconstructed of a material having a temperature-actuated shape memory,said control member having an initial shape and being deformable to adistorted shape when its temperature is below a preselected transitiontemperature and reverting to said initial shape as a result of saidtemperature-actuated shape memory when its temperature is above saidtransition temperature, said movable contact being in said firstposition when said control member has said distorted shape and in saidsecond position when said control member has said initial shape,

bias means mounted within said switch housing and engaging said controlmember, said bias means mechanically biasing said control member todeform the same to its distorted shape when the temperature of saidcontrol member is below said transition temperature, and

electrical controlling means disposed within said switch housing andconnected in a second'electrical circuit, said electrical controllingmeans being selectively energizable to control the temperature of saidcontrol member for controlling the shape of said control member wherebythe operative state of said first electrical circuit is controlled inresponse to energization of said second electrical circult.

2. The invention as recited in claim 1 wherein said control member is awire.

3. The invention as recited in claim 1 wherein said control member is adouble-strand wire.

4. The invention as recited in claim 1 wherein said control member is aspring.

5. The invention as recited in claim 1 wherein said control member is abar having a high torsion initial shape and a low torsion distortedshape.

6. The invention as recited in claim 1 wherein said control member is abar having a curved initial shape and a linear distorted shape.

7. The invention as recited in claim 1 wherein said control member is abar having a linear initial shape and a curved distorted shape.

8. The invention as recited in claim 1 wherein said operator meansincludes lever means connected with said movable contact and saidcontrol member whereby said lever means controls the position of saidmovable contact in accordance with the shape of said control member.

9. The invention as recited in claim 1 wherein said control member is awire having a first end connected with said switch housing and a secondend connected with said operating means, the distance between said firstend of said wire and said second end of said wire being greater whensaid wire has said distorted shape than when said wire has said initialshape.

10. The invention as recited in claim 1 wherein said control member is atorsion spring having a loosely coiled initial shape and tightly coileddistorted shape, said torsion spring being directly connected with saidmovable contact.

11. The invention as recited in claim 1 wherein said electricalcontrolling means includes a heating element disposed adjacent saidcontrol member.

12. The invention as recited in claim 1 wherein said electricalcontrolling means includes circuit means connected with said controlmember to pass an electrical current therethrough to internally heatsaid control member.

13. The invention as recited in claim 1 wherein said material is analloy having a composition of 55 percent nickel by weight with theremainder being essentially titanium.

14. A temperature-responsive switch assembly comprising a switchhousing;

a stationary contact secured to said switch housing;

a movable contact disposed adjacent said stationary contact and having aposition in contact with said stationary contact and a position spacedfrom said stationary contact;

means biasing said movable contact toward one of said positions; and

operator means connected with said movable contact to control theposition of said movable contact, said operating means including acoiled compression spring control member having a loosely coiled initialshape and a tightly coiled distorted shape and being constructed of amaterial having a temperature-actuated shape memory, said movablecontact being in said one position when said control member has saiddistorted shape and in the other position when said control member hassaid initial shape and said operator means further including meanscontrolling the temperature of said control member to control the shapeof said control member.

15. The invention as recited in claim 14 wherein said temperaturecontrolling means includes electrical means connected with said coiledspring to pass an electrical current therethrough to internally heatsaid coiled spring.

16. The invention as recited in claim 15 wherein said bias meansincludes a coiled compression spring.

17. The invention as recited in claim 14 wherein said operator meansincludes lever means connected with said movable contact and said coiledspring, and wherein said coiled spring is mounted in compression betweensaid lever means and said switch housing.

18. The invention as recited in claim 17 wherein said bias meansincludes a helical spring mounted in compression between said levermeans and said switch housing.

19. The invention as recited in claim 18 wherein said temperaturecontrolling means includes electrical means connected with said coiledspring to pass an electrical current therethrough to internally heatsaid coiled spring.

20. The invention as recited in claim 18 wherein said temperaturecontrolling means includes a heating element disposed adjacent saidcoiled spring.

21. The invention as recited in claim 17 wherein said lever means has afirst end, a second end connected with said movable contact and a centerportion secured to a fulcrum, said coiled spring being mounted incompression between said first end of said lever means and said switchhousing, and said bias means being mounted in compression between saidsecond end of said lever means and said switch housing.

22. The invention as recited in claim 17 wherein said lever means has afirst end, a second end connected with said movable contact and a centerportion secured to a fulcrum, said coiled spring being mounted intension between said first end of said lever means and said switchhousing, and said bias means is mounted in compression between saidsecond end of said lever means and said switch housing.

23. A temperature-responsive switch assembly comprising a switchhousing;

a stationary contact secured to said switch housing;

a movable contact disposed adjacent said stationary contact and having aposition in contact with said stationary contact and a position spacedfrom said stationary contact;

means biasing said movable contact toward one of said positions andincluding a helical spring; and

operator means connected with said movable contact to control theposition of said movable contact, said operating means including acoiled spring control member having a tightly coiled initial shape and aloosely coiled distorted shape and being constructed of a materialhaving a temperature-actuated shape memory, lever means connected withsaid movable contact and said coiled spring, said coiled spring beingmounted in tension between said lever means and said switch housing, andsaid helical spring being mounted in compression between said switchhousing and said lever means, said movable contact being in said oneposition when said control member has said distorted shape and in theother position when said control member has said initial shape, and saidoperator means further including means controlling the temperature ofsaid control member to control the shape of said control member.

24. The invention as recited in claim 23 wherein said lever means has afirst end connected with said movable contact, a center portion securedto a fulcrum and a second end, said coiled spring being mounted incompression between one side of said second end of said lever means andsaid switch housing and said bias means being mounted in compressionbetween the other side of said second end of said lever means and saidswitch housing.

25. A temperature-responsive switch assembly comprising a switchhousing;

a stationary contact secured to said switch housing;

a movable contact disposed adjacent said stationary contact and having aposition in contact with said stationary contact and a position spacedfrom said stationary contact;

means biasing said movable contact toward one of said positions; and

operator means connected with said movable contact to control theposition of said movable contact, said operating means including atorsion spring control member connected directly with said movablecontact and having a loosely coiled initial shape and a tightly coileddistorted shape and being constructed of a material having atemperature-actuated shape memory, said torsion spring having a firstsection coiled in a first direction, a second section coiled in adirection opposite said first direction, and a central section directlyconnected with said movable contact, said movable contact being in saidone position when said control member has said distorted shape and inthe other position when said control member has said initial shape, andsaid operator means further including means controlling the temperatureof said control member to control the shape of said control member.

26. The invention as recited in claim 25 wherein saidtemperature-controlling means includes electrical means connected withsaid first and second sections of said torsion spring to pass anelectrical current therethrough and internally heat said torsion spring.

27. A temperature-responsive switch assembly comprising a switchhousing;

a stationary contact secured to said switch housing;

a movable contact disposed adjacent said stationary contact and having aposition in contact with said stationary contact and a position spacedfrom said stationary contact;

spring means biasing said movable contact toward one of said positions;and

operator means connected with said movable contact to control theposition of said movable contact, said operating means including atorsion bar control member having a high torsion initial shape and a lowtorsion distorted shape and being constructed of a material having atemperature-actuated shape memory, said movable contact being in saidone position when said control member has said distorted shape and inthe other position when said control member has said initial shape,means connecting said movable contact with said torsion bar, said springmeans being mounted in compression between said con-

1. An electrically operated switch assembly comprising a switch housing;a stationary contact secured to said housing; a movable contact disposedadjacent said stationary contact and having a first position in contactwith said stationary contact and a second position spaced from saidstationary contact; said stationary contact and said movable contactbeing electrically connected in a first electrical circuit having afirst operative state when said movable contact is in said firstposition and a second operative state when said movable Contact is insaid second position; operator means mounted within said housing andconnected with said movable contact, said operator means including acontrol member constructed of a material having a temperature-actuatedshape memory, said control member having an initial shape and beingdeformable to a distorted shape when its temperature is below apreselected transition temperature and reverting to said initial shapeas a result of said temperature-actuated shape memory when itstemperature is above said transition temperature, said movable contactbeing in said first position when said control member has said distortedshape and in said second position when said control member has saidinitial shape, bias means mounted within said switch housing andengaging said control member, said bias means mechanically biasing saidcontrol member to deform the same to its distorted shape when thetemperature of said control member is below said transition temperature,and electrical controlling means disposed within said switch housing andconnected in a second electrical circuit, said electrical controllingmeans being selectively energizable to control the temperature of saidcontrol member for controlling the shape of said control member wherebythe operative state of said first electrical circuit is controlled inresponse to energization of said second electrical circuit.
 2. Theinvention as recited in claim 1 wherein said control member is a wire.3. The invention as recited in claim 1 wherein said control member is adouble-strand wire.
 4. The invention as recited in claim 1 wherein saidcontrol member is a spring.
 5. The invention as recited in claim 1wherein said control member is a bar having a high torsion initial shapeand a low torsion distorted shape.
 6. The invention as recited in claim1 wherein said control member is a bar having a curved initial shape anda linear distorted shape.
 7. The invention as recited in claim 1 whereinsaid control member is a bar having a linear initial shape and a curveddistorted shape.
 8. The invention as recited in claim 1 wherein saidoperator means includes lever means connected with said movable contactand said control member whereby said lever means controls the positionof said movable contact in accordance with the shape of said controlmember.
 9. The invention as recited in claim 1 wherein said controlmember is a wire having a first end connected with said switch housingand a second end connected with said operating means, the distancebetween said first end of said wire and said second end of said wirebeing greater when said wire has said distorted shape than when saidwire has said initial shape.
 10. The invention as recited in claim 1wherein said control member is a torsion spring having a loosely coiledinitial shape and tightly coiled distorted shape, said torsion springbeing directly connected with said movable contact.
 11. The invention asrecited in claim 1 wherein said electrical controlling means includes aheating element disposed adjacent said control member.
 12. The inventionas recited in claim 1 wherein said electrical controlling means includescircuit means connected with said control member to pass an electricalcurrent therethrough to internally heat said control member.
 13. Theinvention as recited in claim 1 wherein said material is an alloy havinga composition of 55 percent nickel by weight with the remainder beingessentially titanium.
 14. A temperature-responsive switch assemblycomprising a switch housing; a stationary contact secured to said switchhousing; a movable contact disposed adjacent said stationary contact andhaving a position in contact with said stationary contact and a positionspaced from said stationary contact; means biasing said movable contacttoward one of said positions; and operator means connected with saidmovable contact to control the position of said movable contact, saidoperating meAns including a coiled compression spring control memberhaving a loosely coiled initial shape and a tightly coiled distortedshape and being constructed of a material having a temperature-actuatedshape memory, said movable contact being in said one position when saidcontrol member has said distorted shape and in the other position whensaid control member has said initial shape and said operator meansfurther including means controlling the temperature of said controlmember to control the shape of said control member.
 15. The invention asrecited in claim 14 wherein said temperature controlling means includeselectrical means connected with said coiled spring to pass an electricalcurrent therethrough to internally heat said coiled spring.
 16. Theinvention as recited in claim 15 wherein said bias means includes acoiled compression spring.
 17. The invention as recited in claim 14wherein said operator means includes lever means connected with saidmovable contact and said coiled spring, and wherein said coiled springis mounted in compression between said lever means and said switchhousing.
 18. The invention as recited in claim 17 wherein said biasmeans includes a helical spring mounted in compression between saidlever means and said switch housing.
 19. The invention as recited inclaim 18 wherein said temperature controlling means includes electricalmeans connected with said coiled spring to pass an electrical currenttherethrough to internally heat said coiled spring.
 20. The invention asrecited in claim 18 wherein said temperature controlling means includesa heating element disposed adjacent said coiled spring.
 21. Theinvention as recited in claim 17 wherein said lever means has a firstend, a second end connected with said movable contact and a centerportion secured to a fulcrum, said coiled spring being mounted incompression between said first end of said lever means and said switchhousing, and said bias means being mounted in compression between saidsecond end of said lever means and said switch housing.
 22. Theinvention as recited in claim 17 wherein said lever means has a firstend, a second end connected with said movable contact and a centerportion secured to a fulcrum, said coiled spring being mounted intension between said first end of said lever means and said switchhousing, and said bias means is mounted in compression between saidsecond end of said lever means and said switch housing.
 23. Atemperature-responsive switch assembly comprising a switch housing; astationary contact secured to said switch housing; a movable contactdisposed adjacent said stationary contact and having a position incontact with said stationary contact and a position spaced from saidstationary contact; means biasing said movable contact toward one ofsaid positions and including a helical spring; and operator meansconnected with said movable contact to control the position of saidmovable contact, said operating means including a coiled spring controlmember having a tightly coiled initial shape and a loosely coileddistorted shape and being constructed of a material having atemperature-actuated shape memory, lever means connected with saidmovable contact and said coiled spring, said coiled spring being mountedin tension between said lever means and said switch housing, and saidhelical spring being mounted in compression between said switch housingand said lever means, said movable contact being in said one positionwhen said control member has said distorted shape and in the otherposition when said control member has said initial shape, and saidoperator means further including means controlling the temperature ofsaid control member to control the shape of said control member.
 24. Theinvention as recited in claim 23 wherein said lever means has a firstend connected with said movable contact, a center portion secured to afulcrum and a second end, said coiled spring being mounted incompressIon between one side of said second end of said lever means andsaid switch housing and said bias means being mounted in compressionbetween the other side of said second end of said lever means and saidswitch housing.
 25. A temperature-responsive switch assembly comprisinga switch housing; a stationary contact secured to said switch housing; amovable contact disposed adjacent said stationary contact and having aposition in contact with said stationary contact and a position spacedfrom said stationary contact; means biasing said movable contact towardone of said positions; and operator means connected with said movablecontact to control the position of said movable contact, said operatingmeans including a torsion spring control member connected directly withsaid movable contact and having a loosely coiled initial shape and atightly coiled distorted shape and being constructed of a materialhaving a temperature-actuated shape memory, said torsion spring having afirst section coiled in a first direction, a second section coiled in adirection opposite said first direction, and a central section directlyconnected with said movable contact, said movable contact being in saidone position when said control member has said distorted shape and inthe other position when said control member has said initial shape, andsaid operator means further including means controlling the temperatureof said control member to control the shape of said control member. 26.The invention as recited in claim 25 wherein saidtemperature-controlling means includes electrical means connected withsaid first and second sections of said torsion spring to pass anelectrical current therethrough and internally heat said torsion spring.27. A temperature-responsive switch assembly comprising a switchhousing; a stationary contact secured to said switch housing; a movablecontact disposed adjacent said stationary contact and having a positionin contact with said stationary contact and a position spaced from saidstationary contact; spring means biasing said movable contact toward oneof said positions; and operator means connected with said movablecontact to control the position of said movable contact, said operatingmeans including a torsion bar control member having a high torsioninitial shape and a low torsion distorted shape and being constructed ofa material having a temperature-actuated shape memory, said movablecontact being in said one position when said control member has saiddistorted shape and in the other position when said control member hassaid initial shape, means connecting said movable contact with saidtorsion bar, said spring means being mounted in compression between saidconnecting means and said switch housing, and said operator meansfurther including means controlling the temperature of said controlmember to control the shape of said control member.
 28. The invention asrecited in claim 27 wherein said temperature-controlling means includesan electrical heating element disposed around said torsion bar.